The G3X system with multiple GDUs (screens) requires configuration as to the function of each GDU, either PFD or MFD. I'm electing to have the left GDU as PFD & the right GDU as MFD (Program 1). This is performed by installing a link between two pins on the PFD J4602 connector.
GDU Left (PFD) J4602 pin 10 (PROGRAM 1) to pin 27 (SIGNAL GROUND)